Chloroplast ultra-structure dynamics of Ginkgo biloba L. leaves during annual growth and development

Changes in ultra-structure in chloroplasts of 10- year-old seeded ginkgo( Ginkgo biloba L.) leaves during expansion and senescence were studied in the field under natural environmental condition. The results showed that the chloroplast ultra-structure changed obviously during leaf expansion,grana thylakoids were increasingly richer,lamellar structure was more developed and neatly arranged,and the photosynthetic apparatus was gradually improved. The chloroplast ultra-structure changed significantly during leaf senescence. As the leaf senesced,the volume of chloroplasts became swollen,the envelope membranes became disrupted,the inclusions became reduced and the granal thylakoids became loose. The chloroplasts changed from ellipses or ship-like shapes to the irregular circles,had damaged in membranes and fewer grana with loose stacks of thylakoids and more and larger osmiophilic granules.With the leaf senescence,the whole structure of chloroplasts became disorganized,the thylakoid membranes became disrupted,the stroma in chloroplasts almost lost,and finally,the chloroplast was completely disintegrated.